The August 11th early edition of PNAS is, to put it mildly, a bit of a downer. New papers point to a gloomy future for ocean life (Jackson 2008), amphibians (Wake and Vredenburg 2008), and the trees of the Amazon (Hubbell et al. 2008). Surprisingly, Paul “Malthus was an optimist” Ehrlich’s piece is perhaps the least depressing- suggesting that a Pacala/Socolow type wedge strategy of massively mobilizing existing science and technologies could successfully mitigate much of the longterm danger facing biodiversity due to actions this century (Ehrlich and Pringle 2008).
It’s worth noting that in all of these papers, climate change is presented as but a single component of overall anthropogenic influence on the environment. That’s something that gets lost sometimes in the meta-narrative of a media subject to the tyranny of the story peg, but something that strengthens the case for mitigation rather than weakens it. Although some environmentalists and activists would like to make the issue as simple as tailpipe GHG emissions directly causing extinctions (and indeed sloppy reporting can paint global warming as the cause of nearly everything), the situation is far from that simple, and more precarious because of it.
Large swaths of our biosphere are already being stressed to the point of extinction by more familiar threats- destruction of habitat, introduction of invasive species, overuse of resources, local pollution, etc. Combine these factors with natural predation, competition for resources, disease, etc. and it easy to see why even a moderate amount of climate disruption due to anthropogenic emissions can have an effect far larger than it would on its own. Chytridiomycosis, for example, is sometimes cited as an alternative to global warming in precipitating the extinction of the Golden Toad (Bufo periglenes), but this ignores the strong implication that climate change is creating a more favorable environment for the chytrid fungus in some tropical areas where amphibian populations are at greatest risk, in addition to directly threatening the toad by increasing cloud height and reducing moisture deposition (Pounds et al. 2006). In this case, the addition of a modest amount of warming into the equation seems to have been enough to drive the Golden Toad over the edge into extinction, even if it was not the sole, direct cause.
Anthropogenic, emissions-driven climate change does not have to lead to an increase of 4°C+ or spawn evermore Cat 5 hurricanes in order to massively, negatively impact an environment already being pushed to the brink. The upshot is that we while we may already be committed to additional warming, we have the knowledge and technology to reduce other anthropogenic (and if necessary natural) stressors while we also begin the process of emissions reductions. Provided of course that we are not drawn into the false dilemma fallacy so favored by the delayers.